Systems and methods for purging a fuel vapor canister

ABSTRACT

A method for an engine is presented, wherein during a first condition, pressurized gas from an engine coolant degas bottle to an ejector positioned in a vent line coupled to a fuel vapor canister; and the contents of the fuel vapor canister are purged to an engine intake. The ejector may draw atmospheric air into the fuel vapor canister, thus enabling purging of the fuel vapor canister even when an engine intake vacuum is below a threshold. In this way, boosted engines and other engines configured to operate with reduced intake vacuum may execute canister purging events that are independent of engine intake pressure.

FIELD

The present description relates generally to methods and systems forcontrolling a vehicle engine to purge the contents of a fuel vaporcanister independently of intake manifold pressure.

BACKGROUND/SUMMARY

In automotive vehicles, fuel vapor may be generated in a fuel tankduring engine operation, over diurnal cycles, and during refuelingevents. Vehicles sold in North America are required to utilize a carboncanister to collect vaporized fuel from the fuel tank, in order toreduce the quantity of fuel vapors released to the atmosphere. Thevapors stored in the canister may then be purged from the canister intothe engine intake manifold for combustion. In this way, fuel vapors maybe recycled to the engine rather than leaked to the environment.

In many examples, pressure differentials within the engine may beutilized to draw fuel vapors from the canister into the intake manifold.For example, engine intake vacuum may be applied to the canister, thusdrawing atmospheric air through the canister and into the engine intake.However, in boosted engines, intake manifold pressure may varysubstantially depending on whether the compressor is operating. Innon-boost conditions, when the compressor is not operating, the intakemanifold may have a negative pressure. In contrast, during boostconditions when the compressor is operating, the intake manifold mayhave a positive pressure. Canister purging in boosted engines must beenabled during both vacuum conditions and boost conditions.

Other attempts to address canister purging in boosted engines includeusing a venturi effect to generate a vacuum using a positive pressuresource. One example approach is shown by Kempf et al. in U.S. Pat. No.9,109,550. Therein, an ejector or venturi is used as a vacuum source ina dual path purging system. An inlet of an ejector may be coupled to anengine intake upstream of a compressor via a first conduit and an outletof the ejector may be coupled to an intake of the engine downstream ofthe compressor via a second conduit. Motive fluid through the ejectorprovides a vacuum at an ejector suction inlet which is coupled to thefuel vapor canister to draw purge air through the fuel vapor canisterduring boosted operation.

However, the inventors herein have recognized potential issues with suchsystems. As one example, the purge path for boost conditions isconsiderably longer than that for non-boost conditions, as the fuelvapor must pass through the intake air compressor and charge air coolerbefore reaching engine intake. The increased path length results in ahydrocarbon transport delay, which increases the risk of enginehesitation during purge events. Additionally, the amount of vacuum thatcan be generated by recirculation flow through an ejector is limited bythe ejector choke flow, resulting in a limited amount of fresh air flowthrough the canister. Further, in many engine conditions, the intakemanifold has neither enough pressure nor vacuum to generate purge airflow via either purge pathway.

In one example, the issues described above may be addressed by a methodfor an engine, wherein during a first condition, pressurized gas from anengine coolant degas bottle to an ejector positioned in a vent linecoupled to a fuel vapor canister; and the contents of the fuel vaporcanister are purged to an engine intake. The ejector may drawatmospheric air into the fuel vapor canister, thus enabling purging ofthe fuel vapor canister even when an engine intake vacuum is below athreshold. In this way, boosted engines and other engines configured tooperate with reduced intake vacuum may execute canister purging eventsthat are independent of engine intake pressure.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows an example engine coupled to a fuel system.

FIG. 2 schematically shows an example cooling system for an engine and avehicle.

FIG. 3 schematically shows a system for purging a fuel vapor canister ofa boosted engine.

FIG. 4 depicts a flow-chart for a high level method for purging a fuelvapor canister of a boosted engine.

FIG. 5 depicts a timeline for operating a fuel system of a boostedengine.

DETAILED DESCRIPTION

The following description relates to systems and methods for purging afuel vapor canister. A fuel vapor canister may be provided as part of afuel system to contain fuel vapor generated in a fuel tank. The contentsof the canister may then be purged to the engine intake for combustion.Typically, this is done by applying an intake vacuum to the fuel vaporcanister, thus drawing fresh air through the canister and desorbingbound fuel vapor. However, in a boosted engine, such as the engine shownin FIG. 1, operation of an intake air compressor may result in positiveintake pressure, making purging in this way impossible. Such a boostedengine may also comprise a cooling system, such as the cooling systemdepicted in FIG. 2. As engine coolant circulates through the engine,heat is drawn from the engine and dissipated at a radiator. A degasbottle may be deposed within the cooling system to remove entrained airfrom circulating coolant. As the coolant heats up, the degas bottle maybuild significant levels of pressure. This pressure may bere-appropriated for canister purging by coupling the degas bottle to anejector at a canister vent line, as shown in FIG. 3. Thus, duringboosted or reduced vacuum conditions, he degas bottle pressure may beflowed to the ejector such that atmospheric air is drawn through thecanister. This enables canister purging methods that are independent ofintake manifold pressure, as depicted by the method of FIG. 4. Thus,emissions can be reduced by opportunistically purging the fuel vaporcanister, as shown in FIG. 5.

FIG. 1 shows a schematic depiction of a hybrid vehicle system 6 that canderive propulsion power from engine system 10 and/or an on-board energystorage device, such as a battery system (not shown). An energyconversion device, such as a generator (not shown), may be operated toabsorb energy from vehicle motion and/or engine operation, and thenconvert the absorbed energy to an energy form suitable for storage bythe energy storage device. Engine system 10 may comprise amulti-cylinder internal combustion engine, which may be included in apropulsion system of an automotive vehicle. Engine 10 may be controlledat least partially by a control system including controller 12 and byinput from a vehicle operator 130 via an input device 132. In thisexample, input device 132 includes an accelerator pedal and a pedalposition sensor 134 for generating a proportional pedal position signalPP.

Engine 10 may include a lower portion of the engine block, indicatedgenerally at 26, which may include a crankcase 28 encasing a crankshaft30 with oil well 32 positioned below the crankshaft. An oil fill port 29may be disposed in crankcase 28 so that oil may be supplied to oil well32. Oil fill port 29 may include an oil cap 33 to seal oil fill port 29when the engine is in operation. A dip stick tube 37 may also bedisposed in crankcase 28 and may include a dipstick 35 for measuring alevel of oil in oil well 32. In addition, crankcase 28 may include aplurality of other orifices for servicing components in crankcase 28.These orifices in crankcase 28 may be maintained closed during engineoperation so that a crankcase ventilation system (described below) mayoperate during engine operation.

The upper portion of engine block 26 may include a combustion chamber(i.e., cylinder) 34. The combustion chamber 34 may include combustionchamber walls 36 with piston 38 positioned therein. Piston 38 may becoupled to crankshaft 30 so that reciprocating motion of the piston istranslated into rotational motion of the crankshaft. Combustion chamber34 may receive fuel from fuel injector 45 (configured herein as a directfuel injector) and intake air from intake manifold 44 which ispositioned downstream of throttle 42. The engine block 26 may alsoinclude an engine coolant temperature (ECT) sensor 46 input into anengine controller 12 (described in more detail below herein).

A throttle 42 may be disposed in the engine intake to control theairflow entering intake manifold 44 and may be preceded upstream bycompressor 50 followed by charge air cooler 52, for example. An airfilter 54 may be positioned upstream of compressor 50 and may filterfresh air entering intake passage 13. The intake air may entercombustion chamber 34 via cam-actuated intake valve system 40. Likewise,combusted exhaust gas may exit combustion chamber 34 via cam-actuatedexhaust valve system 41. In an alternate embodiment, one or more of theintake valve system and the exhaust valve system may be electricallyactuated. Intake air may bypass compressor 50 via compressor bypassconduit 56, during conditions wherein compressor bypass valve (CBV) 55is opened. In this way, pressure buildup at the compressor inlet may berelieved.

Exhaust combustion gases exit the combustion chamber 34 via exhaustpassage 60 located upstream of turbine 62. An exhaust gas sensor 64 maybe disposed along exhaust passage 60 upstream of turbine 62. Turbine 62may be equipped with a wastegate (not shown) bypassing it. Exhaust gassensor 64 may be a suitable sensor for providing an indication ofexhaust gas air/fuel ratio such as a linear oxygen sensor or UEGO(universal or wide-range exhaust gas oxygen), a two-state oxygen sensoror EGO, a HEGO (heated EGO), a NOx, HC, or CO sensor. Exhaust gas sensor64 may be connected with controller 12. Exhaust passage 60 may includeone or more emissions control devices 94, which may be mounted in aclose-coupled position in the exhaust downstream of turbine 62. The oneor more emission control devices may include a three-way catalyst, leanNOx trap, diesel particulate filter, oxidation catalyst, etc.

In the example of FIG. 1, a positive crankcase ventilation (PCV) system16 is coupled to the engine intake so that gases in the crankcase may bevented in a controlled manner from the crankcase. During non-boostedconditions (when manifold pressure (MAP) is less than barometricpressure (BP)), the crankcase ventilation system 16 draws air intocrankcase 28 via a breather or crankcase ventilation tube 74. A firstside 101 of crankcase ventilation tube 74 may be mechanically coupled,or connected, to fresh air intake passage 13 upstream of compressor 50.In some examples, the first side 101 of crankcase ventilation tube 74may be coupled to intake passage 13 downstream of air filter 54 (asshown). In other examples, the crankcase ventilation tube may be coupledto intake passage 13 upstream of air filter 54. A second, opposite side102 of crankcase ventilation tube 74 may be mechanically coupled, orconnected, to crankcase 28 via an oil separator 81.

Crankcase ventilation tube 74 further includes a sensor 77 coupledtherein for providing an estimate about air flowing through crankcaseventilation tube 74 (e.g., flow rate, pressure, etc.). In someembodiments, crankcase vent tube sensor 77 may be a pressure sensor.When configured as a pressure sensor, sensor 77 may be an absolutepressure sensor or a gauge sensor. In an alternate embodiment, sensor 77may be a flow sensor or flow meter. In still another embodiment, sensor77 may be configured as a venturi. In some embodiments, in addition to apressure or flow sensor 77, the crankcase vent tube may optionallyinclude a venturi 75 for sensing flow there-through. In still otherembodiments, pressure sensor 77 may be coupled to a neck of venturi 75to estimate a pressure drop across the venturi. One or more additionalpressure and/or flow sensors may be coupled to the crankcase ventilationsystem at alternate locations. For example, a barometric pressure sensor(BP sensor) 57 may be coupled to intake passage 13, upstream of airfilter 54, for providing an estimate of barometric pressure. In oneexample, where crankcase vent tube sensor 77 is configured as a gaugesensor, BP sensor 57 may be used in conjunction with gauge pressuresensor 77. In some embodiments, pressure sensor 61 may be coupled inintake passage 13 downstream of air filter 54 and upstream of compressor50 to provide an estimate of the compressor inlet pressure (CIP).However, since crankcase vent tube pressure sensor 77 may provide anaccurate estimate of a compressor inlet pressure during elevated engineair flow conditions (such as during engine run-up), the need for adedicated CIP sensor may be reduced. Further still, a pressure sensor 59may be coupled downstream of compressor 50 for providing an estimate ofa throttle inlet pressure (TIP). Any of the above-mentioned pressuresensors may be absolute pressure sensor or gauge sensors.

PCV system 16 also vents gases out of the crankcase and into intakemanifold 44 via a conduit 76 (herein also referred to as PCV line 76).In some examples, PCV line 76 may include a one-way PCV valve 78 (thatis, a passive valve that tends to seal when flow is in the oppositedirection) to provide continual evacuation of crankcase gases frominside the crankcase 28 before connecting to the intake manifold 44. Inone embodiment, the PCV valve may vary its flow restriction in responseto the pressure drop across it (or flow rate through it). However, inother examples PCV line 76 may not include a one-way PCV valve. In stillother examples, the PCV valve may be an electronically controlled valvethat is controlled by controller 12. It will be appreciated that, asused herein, PCV flow refers to the flow of gases through PCV line 76from the crankcase to the intake manifold. Similarly, as used herein,PCV backflow refers to the flow of gases through PCV line 76 from theintake manifold to the crankcase. PCV backflow may occur when intakemanifold pressure is higher than crankcase pressure (e.g., duringboosted engine operation). In some examples, PCV system 16 may beequipped with a check valve for preventing PCV backflow. It will beappreciated that while the depicted example shows PCV valve 78 as apassive valve, this is not meant to be limiting, and in alternateembodiments, PCV valve 78 may be an electronically controlled valve(e.g., a powertrain control module (PCM) controlled valve) wherein acontroller may command a signal to change a position of the valve froman open position (or a position of high flow) to a closed position (or aposition of low flow), or vice versa, or any position there-between.

The gases in crankcase 28 may consist of un-burned fuel, un-combustedair, and fully or partially combusted gases. Further, lubricant mist mayalso be present. As such, various oil separators may be incorporated incrankcase ventilation system 16 to reduce exiting of the oil mist fromthe crankcase through the PCV system. For example, PCV line 76 mayinclude a uni-directional oil separator 80 which filters oil from vaporsexiting crankcase 28 before they re-enter the intake manifold 44.Another oil separator 81 may be disposed in crankcase ventilation tube74 to remove oil from the stream of gases exiting the crankcases duringboosted operation. Additionally, PCV line 76 may also include a vacuumsensor 82 coupled to the PCV system. In other embodiments, a MAP ormanifold vacuum (ManVac) sensor may be located in intake manifold 44.

Engine system 10 further includes one or more vacuum consumption devices98. A mechanical vacuum pump (MVP) 95 is coupled to vacuum consumptiondevice 98 and is configured to provide vacuum for operating or actuatingthe vacuum consumption devices. MVP 95 may be driven mechanically bycrankshaft 30. As such, MVP 95 may be located at least partially withincrankcase 28, for example, coupled to crankcase cover 31. In this way,MVP 95 may receive lubricating oil without requiring additionallubricant routing. In one example, vacuum consumption device 98 may be abrake booster wherein vacuum pump 95 is actuated responsive to vehiclebrake application. For example, the brake booster may include aninternal vacuum reservoir that amplifies a force provided by a vehicleoperator 130 via a brake pedal for applying vehicle brakes (not shown).A position of the brake pedal may be monitored by a brake pedal sensor.MVP 95 may be selectively operated via a control signal from thecontroller 12 to supply at least some vacuum to the brake booster. MVP95 may be coupled to one or more additional vacuum consumption devices,such as a speed control actuator or HVAC system doors. As shown in FIG.1, MVP 95 exhausts into crankcase 28 via exhaust conduit 96.Hydrocarbons present in the crankcase cover near the MVP may thus bebrought into the crankcase. Engine vacuum may be utilized purge thecrankcase hydrocarbons to intake manifold 44. In contrast, if MVP 95were exhausted directly into intake manifold 44, this may bringunmetered fuel into the engine, thus increasing the risk of enginestalling events due to rich fuel vapor slugs.

Engine system 8 is coupled to a fuel system 18. Fuel system 18 includesa fuel tank 20 coupled to a fuel pump 21 and a fuel vapor canister 90.During a fuel tank refueling event, fuel may be pumped into the vehiclefrom an external source through refueling port 25. Fuel tank 20 may holda plurality of fuel blends, including fuel with a range of alcoholconcentrations, such as various gasoline-ethanol blends, including E10,E85, gasoline, etc., and combinations thereof. A fuel level sensor 22located in fuel tank 20 may provide an indication of the fuel level(“Fuel Level Input”) to controller 12. As depicted, fuel level sensor 22may comprise a float connected to a variable resistor. Alternatively,other types of fuel level sensors may be used.

Fuel pump 21 is configured to pressurize fuel delivered to the injectorsof engine 10, such as example injector 45. It will be appreciated thatfuel system 18 may be a return-less fuel system, a return fuel system,or various other types of fuel system. Vapors generated in fuel tank 20may be routed to fuel vapor canister 90, via conduit 93, before beingpurged to engine intake manifold 44.

Fuel vapor canister 90 may be comprised in evaporative emissions system19. Fuel vapor canister 90 is filled with an appropriate adsorbent fortemporarily trapping fuel vapors (including vaporized hydrocarbons)generated during fuel tank refueling operations, as well as diurnalvapors. In one example, the adsorbent used is activated charcoal. Whenpurging conditions are met, such as when the canister is saturated,vapors stored in fuel vapor canister 90 may be purged to engine intakepassage 13 by opening canister purge valve 92. While a single canister90 is shown, it will be appreciated that fuel system 18 may include anynumber of canisters. In one example, canister purge valve 92 may be asolenoid valve wherein opening or closing of the valve is performed viaactuation of a canister purge solenoid.

Canister 90 may include a buffer (or buffer region), each of thecanister and the buffer comprising the adsorbent. The volume of thebuffer may be smaller than (e.g., a fraction of) the volume of canister90. The adsorbent in the buffer may be same as, or different from, theadsorbent in the canister (e.g., both may include charcoal). The buffermay be positioned within canister 90 such that during canister loading,fuel tank vapors are first adsorbed within the buffer, and then when thebuffer is saturated, further fuel tank vapors are adsorbed in thecanister. In comparison, during canister purging, fuel vapors are firstdesorbed from the canister (e.g., to a threshold amount) before beingdesorbed from the buffer. In other words, loading and unloading of thebuffer is not linear with the loading and unloading of the canister. Assuch, the effect of the canister buffer is to dampen any fuel vaporspikes flowing from the fuel tank to the canister, thereby reducing thepossibility of any fuel vapor spikes going to the engine.

Canister 90 includes a vent 86 for routing gases out of the canister 90to the atmosphere when storing, or trapping, fuel vapors from fuel tank20. Vent 86 may also allow fresh air to be drawn into fuel vaporcanister 90 when purging stored fuel vapors to engine intake passage 13via purge line 91 and purge valve 92. While this example shows vent 86communicating with fresh, unheated air, various modifications may alsobe used. Vent 86 may include a canister vent valve 87 to adjust a flowof air and vapors between canister 90 and the atmosphere. The canistervent valve may also be used for diagnostic routines. When included, thevent valve may be opened during fuel vapor storing operations (forexample, during fuel tank refueling and while the engine is not running)so that air, stripped of fuel vapor after having passed through thecanister, can be pushed out to the atmosphere. Likewise, during purgingoperations (for example, during canister regeneration and while theengine is running), the vent valve may be opened to allow a flow offresh air to strip the fuel vapors stored in the canister. In oneexample, canister vent valve 87 may be a solenoid valve wherein openingor closing of the valve is performed via actuation of a canister ventsolenoid. In particular, the canister vent valve may be an open that isclosed upon actuation of the canister vent solenoid. In some examples,an air filter may be coupled in vent 86 between canister vent valve 87and atmosphere.

Hybrid vehicle system 6 may have reduced engine operation times due tothe vehicle being powered by engine system 10 during some conditions,and by the energy storage device under other conditions. While thereduced engine operation times reduce overall carbon emissions from thevehicle, they may also lead to insufficient purging of fuel vapors fromthe vehicle's emission control system. To address this, a fuel tankisolation valve (FTIV) 85 may be optionally included in conduit 93 suchthat fuel tank 20 is coupled to canister 90 via the valve. Duringregular engine operation, isolation valve 85 may be kept closed to limitthe amount of diurnal or “running loss” vapors directed to canister 90from fuel tank 20. During refueling operations, and selected purgingconditions, isolation valve 85 may be temporarily opened, e.g., for aduration, to direct fuel vapors from the fuel tank 20 to canister 90. Byopening the valve during purging conditions when the fuel tank pressureis higher than a threshold (e.g., above a mechanical pressure limit ofthe fuel tank above which the fuel tank and other fuel system componentsmay incur mechanical damage), the refueling vapors may be released intothe canister and the fuel tank pressure may be maintained below pressurelimits. While the depicted example shows isolation valve 85 positionedalong conduit 93, in alternate embodiments, the isolation valve may bemounted on fuel tank 20. The fuel system may be considered to be sealedwhen isolation valve 85 is closed. In embodiments where the fuel systemdoes not include isolation valve 85, the fuel system may be consideredsealed when purge valve 92 and canister vent valve 87 are both closed.

One or more pressure sensors 23 may be coupled to fuel system 18 forproviding an estimate of a fuel system pressure. In one example, thefuel system pressure is a fuel tank pressure, wherein pressure sensor 23is a fuel tank pressure sensor coupled to fuel tank 20 for estimating afuel tank pressure or vacuum level. While the depicted example showspressure sensor 23 directly coupled to fuel tank 20, in alternateembodiments, the pressure sensor may be coupled between the fuel tankand canister 90, specifically between the fuel tank and isolation valve85. In the depicted example, a canister pressure sensor 99 is coupled tocanister vent 86, between canister 90 and canister vent valve 87. Instill other embodiments, a first pressure sensor may be positionedupstream of the isolation valve (between the isolation valve and thecanister) while a second pressure sensor is positioned downstream of theisolation valve (between the isolation valve and the fuel tank), toprovide an estimate of a pressure difference across the valve. In someexamples, a vehicle control system may infer and indicate a fuel systemleak based on changes in a fuel tank pressure during a leak diagnosticroutine. When a pressure sensor is included upstream of isolation valve85, such as canister pressure sensor 99, an evaporative emissions systemleak may be indicated based on changes in canister pressure during aleak diagnostic routine while isolation valve 85 is maintained closed.

One or more temperature sensors 24 may also be coupled to fuel system 18for providing an estimate of a fuel system temperature. In one example,the fuel system temperature is a fuel tank temperature, whereintemperature sensor 24 is a fuel tank temperature sensor coupled to fueltank 20 for estimating a fuel tank temperature. While the depictedexample shows temperature sensor 24 directly coupled to fuel tank 20, inalternate embodiments, the temperature sensor may be coupled between thefuel tank and canister 90. A canister temperature sensor 97 may becoupled to canister 90 and configured to indicate temperature changes ofthe adsorbent material within the canister. As fuel vapor adsorption isan exothermic reaction and fuel vapor desorption is an endothermicreaction, the canister temperature may be used to indicate a quantity offuel vapor adsorbed during a venting event (e.g., during refueling),and/or the quantity of fuel vapor desorbed during a purging operation.The canister temperature may thus be used to infer the canister load,while changes in canister temperature may be used to determine thecapacity and/or integrity of the fuel vapor canister.

Fuel vapors released from canister 90, for example during a purgingoperation, may be directed into engine intake manifold 44 via purge line91. The flow of vapors along purge line 9 may be regulated by canisterpurge valve 92, coupled between the fuel vapor canister and the engineintake. The quantity and rate of vapors released by the canister purgevalve may be determined by the duty cycle of an associated canisterpurge valve solenoid (not shown). As such, the duty cycle of thecanister purge valve solenoid may be determined by the vehicle'spowertrain control module (PCM), such as controller 12, responsive toengine operating conditions, including, for example, engine speed-loadconditions, an air-fuel ratio, a canister load, etc. By commanding thecanister purge valve to be closed, the controller may seal the fuelvapor recovery system from the engine intake. An optional canister checkvalve (not shown) may be included in purge line 91 to prevent intakemanifold pressure from flowing gases in the opposite direction of thepurge flow. As such, the check valve may be necessary if the canisterpurge valve control is not accurately timed or the canister purge valveitself can be forced open by a high intake manifold pressure.

Fuel system 18 may be operated by controller 12 in a plurality of modesby selective adjustment of the various valves and solenoids. Forexample, the fuel system may be operated in a fuel vapor storage mode(e.g., during a fuel tank refueling operation and with the engine notrunning), wherein the controller 12 may open isolation valve 85 andcanister vent valve 87 while closing canister purge valve (CPV) 92 todirect refueling vapors into canister 90 while preventing fuel vaporsfrom being directed into the intake manifold.

As another example, the fuel system may be operated in a refueling mode(e.g., when fuel tank refueling is requested by a vehicle operator),wherein the controller 12 may open isolation valve 85 and canister ventvalve 87, while maintaining canister purge valve 92 closed, todepressurize the fuel tank before allowing enabling fuel to be addedtherein. As such, isolation valve 85 may be kept open during therefueling operation to allow refueling vapors to be stored in thecanister. After refueling is completed, the isolation valve may beclosed.

As yet another example, the fuel system may be operated in a canisterpurging mode (e.g., after an emission control device light-offtemperature has been attained and with the engine running), wherein thecontroller 12 may open canister purge valve 92 and canister vent valvewhile closing isolation valve 85. Herein, the vacuum generated by theintake manifold of the operating engine may be used to draw fresh airthrough vent 86 and through fuel vapor canister 90 to purge the storedfuel vapors into intake manifold 44. In this mode, the purged fuelvapors from the canister are combusted in the engine. The purging may becontinued until the stored fuel vapor amount in the canister is below athreshold. During purging, the learned vapor amount/concentration can beused to determine the amount of fuel vapors stored in the canister, andthen during a later portion of the purging operation (when the canisteris sufficiently purged or empty), the learned vapor amount/concentrationcan be used to estimate a loading state of the fuel vapor canister.

Controller 12 is shown in FIG. 1 as a microcomputer, includingmicroprocessor unit 108, input/output ports 110, an electronic storagemedium for executable programs and calibration values shown as read onlymemory chip 112 in this particular example, random access memory 114,keep alive memory 116, and a data bus. Controller 12 may receive varioussignals from sensors 117 coupled to engine 10, including measurement ofinducted mass air flow (MAF) from mass air flow sensor 58; enginecoolant temperature (ECT) from temperature sensor 46; PCV pressure fromvacuum sensor 82; exhaust gas air/fuel ratio from exhaust gas sensor 64;crankcase vent tube pressure sensor 77, BP sensor 57, CIP sensor 61, TIPsensor 59, etc. Furthermore, controller 12 may monitor and adjust theposition of various actuators 118 based on input received from thevarious sensors. These actuators may include, for example, throttle 42,intake and exhaust valve systems 40, 41, and PCV valve 78. Storagemedium read-only memory 112 can be programmed with computer readabledata representing instructions executable by processor 108 forperforming the methods described below, as well as other variants thatare anticipated but not specifically listed. An example method isdescribed herein with reference to FIG. 4.

Controller 12 may further receive information regarding the location ofthe vehicle from an on-board global positioning system (GPS).Information received from the GPS may include vehicle speed, vehiclealtitude, vehicle position, etc. This information may be used to inferengine operating parameters, such as local barometric pressure.Controller 12 may further be configured to receive information via theinternet or other communication networks. Information received from theGPS may be cross-referenced to information available via the internet todetermine local weather conditions, local vehicle regulations, etc.Controller 12 may use the internet to obtain updated software moduleswhich may be stored in non-transitory memory.

Controller 12 may also be configured to intermittently perform undesiredemissions detection routines on fuel system 18 and/or evaporativeemissions system 19 to confirm that the fuel system and evaporativeemissions system are not degraded. As such, various diagnostic undesiredemissions detection tests may be performed while the engine is off(engine-off undesired emissions test) or while the engine is running(engine-on undesired emissions test). Undesired emissions testsperformed while the engine is running may include applying a negativepressure on the fuel system for a duration (e.g., until a target fueltank vacuum is reached) and then sealing the fuel system whilemonitoring a change in fuel tank pressure (e.g., a rate of change in thevacuum level, or a final pressure value). Undesired emissions testsperformed while the engine is not running may include sealing the fuelsystem following engine shut-off and monitoring a change in fuel tankpressure. This type of undesired emissions test is referred to herein asan engine-off natural vacuum test (EONV). In sealing the fuel systemfollowing engine shut-off, a vacuum will develop in the fuel tank as thetank cools and fuel vapors are condensed to liquid fuel. The amount ofvacuum and/or the rate of vacuum development may be compared to expectedvalues that would occur for an intact system, and/or for a system withbreaches of a predetermined size. Following a vehicle-off event, as heatcontinues to be rejected from the engine into the fuel tank, the fueltank pressure will initially rise. During conditions of relatively highambient temperature, a pressure build above a threshold may beconsidered a passing test.

FIG. 2 shows an example embodiment of a cooling system 205 in a motorvehicle 206 illustrated schematically. Cooling system 205 circulatescoolant through internal combustion engine 210 and through exhaust gasrecirculation (EGR) cooler 254 to absorb waste heat and distributes theheated coolant to radiator 280 and/or heater core 290 via coolant lines282 and 284, respectively.

In particular, FIG. 2 shows cooling system 205 coupled to engine 210 andcirculating engine coolant from engine 210, through EGR cooler 254, andto radiator 280 via engine-driven water pump 286, and back to engine 210via coolant line 282. Engine-driven water pump 286 may be coupled to theengine via front end accessory drive (FEAD) 236, and rotatedproportionally to engine speed via belt, chain, etc. Specifically,engine-driven pump 286 circulates coolant through passages in the engineblock, head, etc., to absorb engine heat, which is then transferred viathe radiator 280 to ambient air. In an example where pump 286 is acentrifugal pump, the pressure (and resulting flow) produced may beproportional to the crankshaft speed, which may be directly proportionalto engine speed. The temperature of the coolant may be regulated by athermostat valve 238, located in the cooling line 282, which may be keptclosed until the coolant reaches a threshold temperature.

Further, fan 292 may be coupled to radiator 280 in order to maintain anairflow through radiator 280 when vehicle 206 is moving slowly orstopped while the engine is running. In some examples, fan speed may becontrolled by controller 212. Alternatively, fan 292 may be coupled toengine-driven water pump 286.

As shown in FIG. 2, engine 210 may include an exhaust gas recirculation(EGR) system 250. EGR system 250 may route a desired portion of exhaustgas from exhaust manifold 248 to intake manifold 244 via EGR passage256. The amount of EGR provided to intake manifold 244 may be varied bycontroller 212 via EGR valve 251. Further, an EGR sensor (not shown) maybe arranged within EGR passage 256 and may provide an indication of oneor more of pressure, temperature, and concentration of the exhaust gas.Alternatively, the EGR may be controlled based on an exhaust oxygensensor and/or and intake oxygen sensor. Under some conditions, EGRsystem 250 may be used to regulate the temperature of the air and fuelmixture within the combustion chamber. EGR system 250 may furtherinclude EGR cooler 254 for cooling exhaust gas 249 being reintroduced toengine 210. In such an embodiment, coolant leaving engine 210 may becirculated through EGR cooler 254 before moving through coolant line 282to radiator 280. A degas bottle 285 may be positioned in coolant line282 upstream of radiator 280 or other suitable position, such asdownstream of radiator 280.

After passing through EGR cooler 254, coolant may flow through coolantline 282, as described above, and/or through coolant line 284 to heatercore 290 where the heat may be transferred to passenger compartment 204,and the coolant flows back to engine 210. In some examples,engine-driven pump 286 may operate to circulate the coolant through bothcoolant lines 282 and 284. In other examples in which a vehicle has ahybrid-electric propulsion system, an electric auxiliary pump 288 may beincluded in the cooling system in addition to the engine-driven pump. Assuch, auxiliary pump 288 may be employed to circulate coolant throughheater core 290 during occasions when engine 210 is off (e.g., electriconly operation) and/or to assist engine-driven pump 286 when the engineis running. Like engine-driven pump 286, auxiliary pump 288 may be acentrifugal pump; however, the pressure (and resulting flow) produced bypump 288 may be proportional to an amount of power supplied to the pumpby energy storage device 226.

In this example embodiment, the hybrid propulsion system includes anenergy conversion device 224, which may include a motor and a generator,among others, and combinations thereof. The energy conversion device 224is further shown coupled to an energy storage device 226, which mayinclude a battery, a capacitor, a flywheel, a pressure vessel, etc. Theenergy conversion device may be operated to absorb energy from vehiclemotion and/or the engine and convert the absorbed energy to an energyform suitable for storage by the energy storage device (e.g., provide agenerator operation). The energy conversion device may also be operatedto supply an output (power, work, torque, speed, etc.) to the drivewheels 220, engine 210 (e.g., provide a motor operation), auxiliary pump288, etc. It should be appreciated that the energy conversion devicemay, in some embodiments, include only a motor, only a generator, orboth a motor and generator, among various other components used forproviding the appropriate conversion of energy between the energystorage device and the vehicle drive wheels and/or engine.

Hybrid-electric propulsion embodiments may include full hybrid systems,in which the vehicle can run on just the engine, just the energyconversion device (e.g., motor), or a combination of both. Assist ormild hybrid configurations may also be employed, in which the engine isthe primary torque source, with the hybrid propulsion system acting toselectively deliver added torque, for example during tip-in or otherconditions. Further still, starter/generator and/or smart alternatorsystems may also be used. Additionally, the various components describedabove may be controlled by vehicle controller 212. Controller 212 maycomprise a portion of a control system 214. Control system 214 is shownreceiving information from a plurality of sensors 216 (various examplesof which are described herein) and sending control signals to aplurality of actuators 281 (various examples of which are describedherein). Controller 212 may be an example of controller 12.

From the above, it should be understood that the exemplaryhybrid-electric propulsion system is capable of various modes ofoperation. In a full hybrid implementation, for example, the propulsionsystem may operate using energy conversion device 224 (e.g., an electricmotor) as the only torque source propelling the vehicle. This “electriconly” mode of operation may be employed during braking, low speeds,while stopped at traffic lights, etc. In another mode, engine 210 isturned on, and acts as the only torque source powering drive wheel 220.In still another mode, which may be referred to as an “assist” mode, thehybrid propulsion system may supplement and act in cooperation with thetorque provided by engine 210. As indicated above, energy conversiondevice 224 may also operate in a generator mode, in which torque isabsorbed from engine 210 and/or the transmission. Furthermore, energyconversion device 224 may act to augment or absorb torque duringtransitions of engine 210 between different combustion modes (e.g.,during transitions between a spark ignition mode and a compressionignition mode).

It is to be understood that the hybrid vehicle configuration describedabove is exemplary and other vehicle configurations are within the scopeof this disclosure. For example, the vehicle system may be a non-hybridsystem where power for propulsion is only derived from the engine andnot from an energy conversion device.

FIG. 3 schematically shows a portion of a fuel system 300 comprising afuel vapor canister 302. Fuel system 300 may be an example of fuelsystem 18, while fuel vapor canister 302 may be an example of fuel vaporcanister 90. Canister 302 may comprise a load conduit 306 that may becoupled to a fuel tank via a fuel tank ventilation line 308. A fuel tankisolation valve (FTIV) 310 may be deposed in fuel tank ventilation line308 in order to regulate the flow of fuel vapor between the fuel tankand load conduit 306. Load conduit 306 may be coupled to load port 312,traversing an outer wall of canister 302. In some examples, load port312 may be coupled to canister buffer 314.

Canister 302 may further comprise a fresh air conduit 316 that may becoupled to atmosphere via canister vent line 318. A canister vent valve(CVV) 320 may be deposed in vent line 318 in order to regulate the flowof air and gasses between atmosphere and fresh air conduit 316. Freshair conduit 316 may be coupled to fresh air port 322, traversing anouter wall of canister 302. In some examples, fresh air port 322 may becoupled to bleed element 324.

Canister 302 may further comprise a purge conduit 326 that may becoupled to an engine intake via purge line 328. A canister purge valve(CPV) 330 may be deposed in purge line 328 in order to regulate the flowof purge gasses between the engine intake and purge conduit 326. Purgeconduit 326 may be coupled to purge port 332, traversing an outer wallof canister 302. In some examples, purge port 322 may be coupled tocarbon dust filter 334 and/or canister buffer 314.

Load port 312, fresh air port 322, and purge port 332 may extend into acentral cavity 336 of canister 302 in order to facilitate the flow ofgasses in and out of canister 302. As described with regard to canister222, the central cavity 336 of canister 302 may be filled with anadsorbent material 338, which may comprise any suitable material fortemporarily trapping fuel vapors (including vaporized hydrocarbons)generated during fuel tank refueling operations, as well as diurnalvapors. In one example, adsorbent material 338 is activated charcoalpellets. Bleed element 324 may also comprise an adsorbent, which may bethe same adsorbent as that of adsorbent material 338. However, as bleedelement 324 may function to prevent bleed emissions during prolongedengine off soaks wherein fuel vapor may migrate within adsorbent 338towards vent port 322, bleed element 324 may bind fuel vapor moretightly than adsorbent 338, and/or may comprise a restrictive pathway toreduce air flow through the bleed element (e.g., a honeycomb structure).

Fuel vapor entering central cavity 336 via load port 312 may bind toadsorbent material 338, while gasses stripped of fuel vapor may thenexit canister 302 via fresh air port 322. In some examples, a partition340 may extend between fresh air port 322 and ports 312 and 332 tofacilitate distribution of fuel vapor and fresh air throughout centralcavity 336, though partition 340 may not completely isolate the freshair side of canister 302 from the load side.

During non-boosted engine operation, or when a threshold vacuum existsin the engine intake, a standard canister purging method may be used.Therein, CVV 320 may be opened, coupling canister purge port 322 toatmosphere. FTIV 310 may be closed, preventing fuel vapor from escapingthe fuel tank. CPV 330 may then be opened, and the engine intake vacuumwill draw atmospheric air through the central cavity 336 of canister302, desorbing hydrocarbons bound to adsorbent 338, which then exit thecanister through purge port 332 and are flowed to engine intake alongpurge line 328.

However, during boosted conditions, or other engine operating conditionswhere engine intake vacuum is minimal (e.g., wide-open throttle), thisprimary purge path is insufficient to draw fresh air through thecanister. As such, an additional means of generating airflow through thecanister and towards engine intake is needed. An ejector 342 may becoupled to vent line 318 as shown in FIG. 3. An inlet (342 a) of ejector342 may be coupled to a positive pressure source. A suction inlet (342b) may be coupled to vent line 318 in a position to draw atmospheric airinto vent line 318 when CVV 320 is opened and a positive pressure isbeing flowed into inlet 342 a. Atmospheric air may then exit ejector 342via outlet 342 c and flow through vent line 318 into fuel vapor canister302 via fresh air port 322.

Fuel system 300 may further include degas bottle 344. Degas bottle 344may be coupled to a vehicle cooling system, in the manner of degasbottle 285 of cooling system 205 shown in FIG. 2. Degas bottle 344 maycomprise other elements not shown in FIG. 3, such as an over-pressurecheck valve, a temperature sensor, a pressure sensor, etc. Degas bottle344 may comprise a pressurized reservoir serving to separate entrainedair from engine coolant. When the temperature of coolant in the coolantsystem rises, pressure may rise in the degas bottle 344. The pressurewithin degas bottle 344 may thus be utilized as the positive pressuresource coupled to inlet 342 a of ejector 342.

In one example, degas bottle 344 may be coupled to ejector 342 via degasrouting line 346. Degas routing line 346 may be coupled to a port at anupper surface of degas bottle 344, such that a level of engine coolantis maintained below the degas routing line port. Vapor flow betweendegas bottle 344 and ejector 342 may be controlled by a degas pressurerouting valve 352 disposed in degas routing line 346. Further, degasrouting line 346 may include filter 348 for preventing the flow ofdebris from degas bottle 344 to canister vent line 318, and a liquidfluid trap 350, designed to trap residual liquid escaping the degasbottle 345, thus preventing coolant from entering the fuel system viacanister vent line 318. As indicated by arrows in FIG. 3, pressureexpelled from degas bottle 344 draws fresh air into vent line 318 viaejector 342, thus allowing for the purging of canister 302 duringboosted or minimal vacuum conditions. The hydrocarbon transport pathremains the same as during intake vacuum mediated purging. Further, theheated coolant vapor in the degas bottle increases purge efficiency, asdesorption of fuel vapor is an endothermic reaction.

As shown in FIG. 3, ejector 342 is coupled to vent line 318 between CVV320 and fresh air conduit 316. However, other ejector placementlocations are possible. For example, ejector 342 may be coupled to ventline 318 between CVV 320 and atmosphere. Alternatively, ejector 342 maybe coupled to purge line 328, such that suction inlet 342 b is in aposition to draw air through purge conduit 326, while outlet 342 c is ina position to direct purge gasses through CPV 330 and towards engineintake.

Turning to FIG. 4, a flow chart for a high level method 400 forperforming fuel vapor purging during boosted and non-boosted engineoperating conditions is shown. Instructions for carrying out method 400and the rest of the methods included herein may be executed by acontroller, such as controller 12 shown in FIG. 1 based on instructionsstored on a memory of the controller and in conjunction with signalsreceived from sensors of the engine system, such as the sensorsdescribed above with reference to FIGS. 1-3. The controller may employengine actuators of the engine system to adjust engine operation,according to the methods described below. Method 400 will be describedherein with reference to the components and systems depicted in FIGS.1-3, though it should be understood that method 400 or similar methodsmay be applied to other systems without departing from the scope of thisdisclosure.

Method 400 begins at 405, where the method includes evaluating operatingconditions. Operating conditions may be measured, estimated, and/orinferred. Operating conditions may include various ambient conditions,such as temperature, humidity, and barometric pressure, various engineconditions, such as engine operating status, engine speed, engine load,etc., various fuel system conditions, such as fuel level, fuel tankpressure, fuel vapor canister load status, etc., as well as othervehicle system and sub-system conditions. Continuing at 410, method 400includes determining whether a canister load is greater than athreshold. The canister load may be measured, estimated, or inferred.For example, the canister load may be based on an amount of fuel vaporadsorbed by the canister since a previous canister purging event asdetermined via canister temperature changes, fuel tank pressure changes,hydrocarbon sensor readings, etc. The canister load threshold may bepredetermined or may be based on current operating conditions. If thecanister load is below the threshold, method 400 proceeds to 415, andincludes maintaining the current status of the evaporative emissionssystem and the fuel system. Method 400 may then end.

If the canister load is above the threshold, method 400 proceeds to 420,and includes determining whether purge conditions are met. Determiningwhether purge conditions are met may include evaluating engine operatingstatus, engine intake vacuum level, and commanded A/F ratio, anddetermining whether a purge event can be performed without disruptingengine operations. If purge conditions are not met, method 400 mayproceed to 425. At 425, method 400 may include maintaining the currentstatus of the evaporative emissions control and fuel systems until purgeconditions are met. Method 400 may then end. Although purge conditionsmay be met at the beginning of method 400, if operating conditionschange during the execution of method 400, the purge operation may beaborted, and the emissions control system and fuel system restored to adefault conformation. A flag may be set at a controller, such ascontroller 12 to follow up when purge conditions are again met. Method400 may then end.

If purge conditions are met, method 400 proceeds to 430. At 430, method400 includes determining whether an intake manifold vacuum is greaterthan a threshold. Intake manifold vacuum may be measured using amanifold adjusted pressure sensor, such as MAP sensor XX shown inFIG. 1. The vacuum threshold may be pre-determined, or may be based oncurrent operating conditions. The vacuum threshold may represent aminimum negative pressure required to draw a quantity of fresh airthrough the fuel vapor canister sufficient to purge fuel vapor to theengine intake. In some examples, it may further be determined whetherboosted conditions are present or imminent. The boosted conditions mayinclude conditions during which a compressor (such as compressor 50shown in FIG. 1) is in operation. As an example, boosted conditions maybe determined to be present when a manifold absolute pressure is greaterthan a barometric pressure by a threshold amount. Imminent boostedconditions may include engine and vehicle conditions that indicate theair intake compressor is likely to be activated. Such a condition may bebased on engine load, engine speed, road grade, etc.

If intake manifold vacuum is greater than the threshold, method 400proceeds to 435, and includes closing the FTIV or maintaining the FTIVclosed, in order to prevent drawing fuel tank vapors into the engineintake during the purge event, and opening the CVV or maintaining theCVV open, in order to allow for fresh air to be drawn through thecanister. At 440, method 400 includes maintaining the degas pressurerouting valve closed. Continuing at 445, method 400 includes opening theCPV, thereby coupling the engine intake to the fuel vapor canister, andpurging the contents of the fuel vapor canister to the engine intake.The duty cycle of the CPV may be ramped up gradually, as the purge gasconcentration is learned and updated.

This conformation may be maintained for a duration, eitherpre-determined or based on current operating conditions. For example,the conformation may be maintained until the purge gas concentrationdecreases below a threshold, or the canister load is otherwisedetermined to be below a threshold. Method 400 then proceeds to 450, andincludes restoring the status of the fuel system. For example, the CPVmay be closed, and the FTIV placed in a default (non-purging)conformation. Continuing at 455, method 400 includes updating a canisterload at the controller. A purge schedule may be updated based on theupdated canister load. Method 400 may then end.

Returning to 430, if manifold vacuum is less than the threshold, method400 then proceeds to 460, and includes closing the FTIV and opening theCVV. Continuing at 465, method 400 includes opening a degas pressurerouting valve, such as routing valve 352 as shown in FIG. 3. Opening thedegas pressure routing valve allows pressurized gas to exit the degasbottle, flowing through an ejector coupled to canister vent line, thuscreating a vacuum and drawing fresh air through the fuel vapor canister.In some examples, the duty cycle of the degas pressure routing valve maybe based on a degas bottle pressure and/or an intake manifold pressure.Method 400 then proceeds to 445, and includes opening the CPV andpurging the contents of the fuel vapor canister as described above.Following the purge event, the fuel system status is restored to anon-purging conformation, including a closed CPV and a closed degaspressure routing valve. A canister load is then updated. Method 400 maythen end.

FIG. 5 shows an example timeline 500 for operating a fuel system for aboosted engine. In particular, timeline 500 shows example purge routinesduring boosted and non-boosted conditions for a fuel system comprising acanister vent ejector coupled to a degas bottle, such as the fuel systemdescribed herein and with regard to FIG. 3, using the method describedherein and with regard to FIG. 4. Timeline 500 includes plot 510,indicating a manifold adjusted pressure (MAP) over time. Line 515represents a threshold manifold vacuum for purging a fuel vapor canistervia intake vacuum. Timeline 500 further includes plot 520, indicating anintake air compressor status over time; plot 530, indicating a canistervent valve (CVV) status over time; and plot 540, indicating a fuel tankisolation valve (FTIV) status over time. Timeline 500 further includesplot 550, indicating a canister purge valve (CPV) status over time; andplot 560, indicating a degas bottle routing valve (DBRV) status overtime. Finally, timeline 500 includes plot 570, indicating a fuel vaporcanister load over time, and wherein line 575 represents a thresholdcanister load where purging is indicated.

At time t₀, the engine is operating under non-boost conditions. Theintake air compressor is off, as indicated by plot 520. The CVV is open,as indicated by plot 530, while the FTIV, CPV, and DBRV are all closed,as indicated by plots 540, 550, and 560, respectively. As shown by plot570, the canister load is above the threshold for purging represented byline 575. At time t₁, the manifold adjusted pressure, as indicated byplot 510 decreases below the threshold for canister purging via engineintake vacuum represented by line 515. As such, a canister purging eventis initiated. The CPV is opened, while the CVV is maintained open, andthe FTIV and DBRV are maintained closed. In this conformation, engineintake vacuum is applied to the canister across the open CPV, drawingfresh air through the open CVV. As such, the canister load decreasesfrom time t₁ to time t₂. At time t₂, the purging event ends, and the CPVis closed.

At time t₃, the intake air compressor is activated, as the engineswitches to a boosted mode. Accordingly, the manifold adjusted pressureincreases above atmospheric pressure. At time t₄, a fuel tank ventingevent is initiated by opening the FTIV. Fuel vapor is flowed into thefuel vapor canister, and gasses stripped of fuel vapor are flowed toatmosphere through the open CVV. The CPV is maintained closed,preventing fuel vapor from reaching intake. The canister load thusincreases from time t₄ to time t₅, when the FTIV is closed.

At time t₅, the canister load is above the threshold for purgingrepresented by line 575. The intake air compressor is maintained on, andthe MAP is above the threshold for engine intake vacuum based canisterpurging. Accordingly, at time t₆, the CPV and DBRV are opened while theCVV is maintained open. In this conformation, pressurized gas from thedegas bottle is released and flowed through a canister vent ejector,thus creating a vacuum and drawing fresh air through the open CVV andinto the fuel vapor canister. As such, the canister load decreases fromtime t₆ to time t₇, when the CPV and DBRV are closed, thus ending thepurging event.

The systems described herein and with reference to FIGS. 1-3, along withthe methods described herein and with reference to FIG. 4 may enable oneor more systems and one or more methods. In one example, a method for anengine is presented, comprising: during a first condition, flowingpressurized gas from an engine coolant degas bottle to an ejectorpositioned in a vent line coupled to a fuel vapor canister; and purgingcontents of the fuel vapor canister to an engine intake. In such amethod, or any other method, the first condition may additionally oralternatively comprise an intake manifold adjusted pressure greater thana threshold. In any of the preceding methods, or any other methods, thefirst condition may additionally or alternatively comprise a boostedengine condition. In any of the preceding examples, or any otherexamples, purging contents of the fuel vapor canister to an engineintake may additionally or alternatively comprise opening a canisterpurge valve and maintaining a canister vent valve open. In any of thepreceding examples, or any other examples, flowing pressurized gas froman engine coolant degas bottle to an ejector may additionally oralternatively comprise opening a degas bottle routing valve deposedwithin a degas routing line coupled between the degas bottle and aninlet of the ejector. In any of the preceding examples, or any otherexamples, a suction inlet of the ejector may additionally oralternatively be coupled within the vent line so as to draw atmosphericair through the vent line responsive to pressurized gas being flowedinto the ejector. In any of the preceding examples, or any otherexamples, an outlet of the ejector may additionally or alternatively becoupled within the vent line so as to direct atmospheric air drawnthrough the vent line towards a fresh air port of the fuel vaporcanister. In any of the preceding examples, or any other example, themethod may additionally or alternatively comprise during a secondcondition, maintaining the degas bottle routing valve closed; andpurging contents of the fuel vapor canister to the engine intake. In anyof the preceding examples, or any other example, the second conditionmay additionally or alternatively comprise an engine intake vacuumgreater than a threshold. The technical effect of implementing thismethod is a decreased reliance on engine intake vacuum to facilitatefuel vapor canister purging. In this way, the fuel vapor canister may bepurged during boosted conditions or other low-manifold vacuumconditions, thereby reducing vehicle emissions.

In another example, an engine system is presented, comprising an ejectorcoupled between a fuel vapor canister fresh air port and atmosphere; anda pressurized gas source selectively coupled to an inlet of the ejector.In such an engine system, or any other engine system, the pressurizedgas source may additionally or alternatively be an engine coolant degasbottle. In any of the preceding examples, or any other examples, theengine system may additionally or alternatively comprise a degas routingline coupled between the engine coolant degas bottle and the inlet ofthe ejector; and a degas bottle routing valve deposed in the degasrouting line, the degas bottle routing valve selectively operable topermit flow of pressurized gas between the engine coolant degas bottleand the inlet of the ejector. In any of the preceding examples, or anyother examples, the engine system may additionally or alternativelycomprise a filter deposed within the degas routing line between theengine coolant degas bottle and the degas bottle routing valve. In anyof the preceding examples, or any other examples, the engine system mayadditionally or alternatively comprise a liquid fluid trap coupled tothe degas routing line between the engine coolant degas bottle and thedegas bottle routing valve. In any of the preceding examples, or anyother examples, the engine system may additionally or alternativelycomprise a canister vent line coupled between the fuel vapor canisterfresh air port and atmosphere; and a canister vent valve deposed withinthe canister vent line, and wherein the ejector is coupled to thecanister vent line between the fuel vapor canister fresh air port andthe canister vent valve. In any of the preceding examples, or any otherexamples, the ejector may additionally or alternatively comprise asuction inlet of coupled within the canister vent line so as to drawatmospheric air through the canister vent line responsive to pressurizedgas being flowed into the inlet of the ejector, and wherein the ejectorfurther comprises an outlet coupled within the canister vent line so asto direct atmospheric air drawn through the canister vent line towardsthe fuel vapor canister fresh air port. The technical effect ofimplementing this system is a reduction in engine stalling events. Inboosted engines, the fuel vapor canister may be purged by placing anejector within a recirculation line between an outlet of an intake aircompressor and an inlet of the intake air compressor, and utilizingvacuum generated by the ejector to draw fresh air through the fuel vaporcanister. This increases the path length of the purge route, increasingthe risk of miscalculating fuel vapor concentration at the engineintake. By generating vacuum downstream of the canister, the typicalpurge path length may be maintained, and fuel vapor entering the engineintake may be accurately metered.

In yet another example, a system for an engine is presented, comprising:a coolant system configured to circulate engine coolant through theengine via one or more coolant lines; a degas bottle coupled to at leastone coolant line, the degas bottle configured to separate entrained airfrom circulating engine coolant; a degas bottle routing valve coupledwithin a degas bottle routing line, the degas bottle routing valveoperable to selectively flow pressurized gas from the degas bottlethrough the degas bottle routing line; and an ejector having an inletcoupled to the degas bottle routing line, the ejector positioned to drawatmospheric air through a suction inlet responsive to pressurized gasflowing into the inlet of the injector, such that the atmospheric airpasses through a fuel vapor canister coupled to an intake of the engine.In such an example, or any other example, the suction inlet of theejector may additionally or alternatively be coupled to a vent linedeposed between the fuel vapor canister and atmosphere. In any of thepreceding examples, or any other example, the system may additionally oralternatively comprise a filter deposed within the degas routing linebetween the engine coolant degas bottle and the degas bottle routingvalve; and a liquid fluid trap coupled to the degas routing line betweenthe filter and the degas bottle routing valve. In any of the precedingexamples, or any other example, the system may additionally oralternatively comprise an intake air compressor; and a purge linecoupled between the fuel vapor canister and the intake of the enginedownstream of the intake air compressor, and wherein the purge line isnot coupled to the intake of the engine upstream of the intake aircompressor. The technical effect of implanting this system is anincrease in purge efficiency. By utilizing degas bottle pressure, airheated by engine coolant is directed towards the fuel vapor canister. Asdesorption of hydrocarbons from activated carbon is an endothermicreaction, the increased temperature of purge air increases the amount ofhydrocarbons purged per unit of purge air.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. A method for an engine, comprising: duringa first condition, flowing pressurized gas from an engine coolant degasbottle to an ejector positioned in a vent line coupled to a fuel vaporcanister; and purging contents of the fuel vapor canister to an engineintake.
 2. The method of claim 1, wherein the first condition comprisesan intake manifold adjusted pressure greater than a threshold.
 3. Themethod of claim 2, wherein the first condition further comprises aboosted engine condition.
 4. The method of claim 1, wherein purgingcontents of the fuel vapor canister to an engine intake comprisesopening a canister purge valve and maintaining a canister vent valveopen.
 5. The method of claim 4, wherein flowing pressurized gas from theengine coolant degas bottle to an ejector comprises opening a degasbottle routing valve disposed within a degas routing line coupledbetween the degas bottle and an inlet of the ejector.
 6. The method ofclaim 5, wherein a suction inlet of the ejector is coupled within thevent line so as to draw atmospheric air through the vent line responsiveto pressurized gas being flowed into the ejector.
 7. The method of claim6, wherein an outlet of the ejector is coupled within the vent line soas to direct atmospheric air drawn through the vent line towards a freshair port of the fuel vapor canister.
 8. The method of claim 5, furthercomprising: during a second condition, maintaining the degas bottlerouting valve closed; and purging contents of the fuel vapor canister tothe engine intake.
 9. The method of claim 8, wherein the secondcondition comprises an engine intake vacuum greater than a threshold.10. A system for an engine, comprising: a coolant system configured tocirculate engine coolant through the engine via one or more coolantlines; a degas bottle coupled to at least one coolant line, the degasbottle configured to separate entrained air from circulating enginecoolant; a degas bottle routing valve coupled within a degas bottlerouting line, the degas bottle routing valve operable to selectivelyflow pressurized gas from the degas bottle through the degas bottlerouting line; and an ejector having an inlet coupled to the degas bottlerouting line, the ejector positioned to draw atmospheric air through asuction inlet responsive to pressurized gas flowing into the inlet ofthe ejector, such that the atmospheric air passes through a fuel vaporcanister coupled to an intake of the engine.
 11. The system of claim 10,wherein the suction inlet of the ejector is coupled to a vent linedisposed between the fuel vapor canister and atmosphere.
 12. The systemof claim 10, further comprising: a filter disposed within the degasrouting line between the engine coolant degas bottle and the degasbottle routing valve; and a liquid fluid trap coupled to the degasrouting line between the filter and the degas bottle routing valve. 13.The system of claim 10, further comprising: an intake air compressor;and a purge line coupled between the fuel vapor canister and the intakeof the engine downstream of the intake air compressor, and wherein thepurge line is not coupled to the intake of the engine upstream of theintake air compressor.